1. Field of the Invention
The present invention generally relates to a variable reluctance resolver type apparatus for detecting an angle of rotation (e.g. angular position of a rotating member such as a shaft of a machine). More particularly, the present invention is concerned with a rotation angle detecting apparatus having a foldable or bendable laminated core.
2. Description of Related Art
For having better understanding of the concept underlying the present invention, description will first be made of a conventional rotation angle detecting apparatus known heretofore. FIG. 20 of the accompanying drawings is a perspective view showing an annular stator of a conventional rotation angle detecting apparatus which is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 136703/2001 (JP-A-13-136703). In FIG. 20, reference numeral 101 denotes an annular stator implemented substantially in the form of an annulus of a laminated or sintered integral structure or the like. Disposed on and along both side surfaces of the annular stator 101 are a pair of insulation caps 106 each of which is formed of an insulation material such as a resin or the like in a ring-like shape and between which the annular stator 101 is fixedly mounted, being sandwiched. Incidentally, in FIG. 20, one of the insulation caps 106 is omitted from illustration.
A plurality of tooth portions 105a and a plurality of slots 105b are formed alternately with each other in an inner side surface of the annular stator 101 while formed in the insulation cap 106 are projecting portions 106a which correspond to the tooth portions 105a, respectively, and slot portions 106b which correspond to the slots 105b, respectively. In this manner, each of the tooth portions 105a as well as each of the slots 105b are retained in the state electrically insulated from each other by means of the projecting portions 106a and the slot portions 106b, respectively.
An exciting winding and output windings are wound around an outer periphery of each of the projecting portions 106a provided in association with the tooth portions 105a, respectively, and crossover wires (not shown) interconnecting the windings are wound around crossover wire guide members 106c, respectively, which are formed integrally with the insulation cap 106 between the tooth portions 105a, respectively.
Formed integrally with the insulation caps 106 at an outer peripheral portion thereof is a connector 107 which is provided with a plurality of terminals 107a. Lead wires connected to the individual terminals 107a, respectively, are led out from the connector 107 in the form of a cable. Further, end portions of the individual windings wound around the outer peripheries of the individual projecting portions 106a are electrically and mechanically connected to the terminals 107a, respectively.
Disposed rotatably at a center position of the annular stator 101 implemented in the structure described above is a rotor (not shown in FIG. 20) which is constituted solely by an iron core having no winding mounted thereof. In this conjunction, it is to be noted that the rotor is so disposed that the center thereof is deviated from that of the annular stator 101. To say in another way, the rotor is so structured or arranged that gap permeance prevailing between the rotor and the tooth portions 105a of the annular stator 101 changes sinusoidally as a function of a rotation angle of the rotor relative to the stator. Incidentally, in place of disposing eccentrically the circular rotor relative to the annular stator 101 as mentioned above, the rotor may be disposed concentrically with the annular stator 101 by forming the rotor in a non-circular shape, substantially to the same effect.
In operation of the rotation angle detecting apparatus of the structure described above, an electric voltage having a predetermined sinusoidal waveform is applied to the exciting winding mentioned previously. In this state, the rotor mounted on a rotatable shaft of an instrument or a machine is rotated, gap permeance prevailing between the annular stator 101 and the rotor changes, as a result of which the amplitude of the output voltage of the output winding and the phase thereof relative to the exciting signal change correspondingly. Thus, by processing the signal derived from the output winding by means of a proper detecting circuit, it is possible to detect the rotation angle (or angular position) of the rotating shaft mentioned above.
The conventional rotation angle detecting apparatus however suffers a problem that because of the structure of the annular stator 101 descried above, work involved in forming the windings becomes very troublesome when the apparatus is to be implemented in a small or miniature size, making it practically difficult to manufacture the rotation angle detecting apparatus of a small size. Besides, a lot of time is taken for forming the winding, incurring a problem that the manufacturing cost increases.